Field of the Invention
The invention relates to a paper sheet guiding cylinder for a printing machine that is mounted in side frames of the machine, and has a driving connection to a printing machine drive, a casing surface provided with through holes, means for supplying blowing air into the paper sheet guiding cylinder, and means located inside the paper sheet guiding cylinder for deflecting the blowing air in the direction of the cylindrical casing.
Paper sheet guiding cylinders are known in the art to be used in printing machines to transport printed paper sheets between printing units or in a deliver section. The paper sheet should also be guided stably and smear-free with printed sheets having a printed side which is oriented towards the outer casing of the latter sheet guiding cylinder. The outer casings are also known in the art to be provided with expensive special coatings. The paper sheet guiding cylinders are additionally known in the art to be provided with blowing air passed from their interior to the outer casing and to the exterior by means of blow jets being oriented towards and connected non-rotatably to the paper sheet guiding cylinder and with a complex external blowing air supply. The blowing air jets only cover a certain part of the paper sheet guiding area. In order to cover a larger part of the paper sheet guiding area it is necessary to place several rows of blow jets in close succession one after the other. The external blowing air supply requires a large number of sealing means, air supply means and a complex blowing air control system.
According to German Published, Non-Prosecuted Application DE 36 38 452 A1 it is also known to place air blades for deflecting the blowing air to the exterior inside a paper sheet guiding cylinder and to non-rotatably connect the air blades to the paper sheet guiding cylinder. It is possible to use such air blades to adequately supply the cylinder surface with an air cushion at high speeds in such a way that the printed side of a paper sheet does not come into contact with the outer casing of the paper sheet guiding cylinder and therefore to largely avoid smearing effects. However, when printing conditions are altered and at low speeds in particular, the air supply is not enough to prevent further touching contacts. Therefore, wide working areas, for example proof printing or production run printing of highly accurate special orders that are usually printed at slow speeds, cannot be reliably transported free from smears. On one hand, if the machine stops suddenly the paper sheets can simply collapse under their own weight and in critical areas can even stick to the outer casings of the paper sheet guiding cylinder. On the other hand, at very high speeds that go beyond the narrow speed range of stable smear-free paper sheet guiding, the air cushion easily becomes too thick and additionally because of breakaway effects of the flow, the paper sheets can flutter and can also contact paper sheet guiding surfaces with their printed sides.